New AMOLED Pixel Circuit to Compensate Characteristics Variations of LTPS TFTs and Voltage Drop

A voltage-programmed AMOLED pixel circuit to compensate the electrical characteristics variations of low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) is proposed. This circuit features a voltage charging process of the storage capacitor (i.e. C1) in the compensation process, which is strongly dependent on the threshold voltage and mobility of the driving TFT, and a charge sharing process between C1 and the gate electrode of the driving transistor. The proposed circuit requires relative simple external driving circuits as only scanning signals of two adjacent gate lines (i.e. SCAN[n] and SCAN[n+1]) and one light emitting signal (i.e. EM[n]) are used. In addition, the voltage drop of the power line can also be compensated by this new circuit. The simulation results demonstrate that the relative current error rates are less than 7.4% and 6% for Vth variations of ±0.3V and mobility variations of ±10%, respectively.